Salicylates, like heat shock and UV damage, induce a panoply of changes in E.coli including (but not limited to): the induction of resistance to certain classes of antibiotics and sensitivity to others; alteration in outer membrane protein composition; and increase sensitivity to Cd++. Some of these effects may be of the weak acid variety, but the majority are not as they are also induced by salicyl alcohol. In an attempt to dissect and define the action of salicyl alcohol on E. coli, we have constructed two libraries of 10/5 independent transpositional events, each containing the lac Z gene (with and without translational initiation signals) inserted at random about the E. coli genome. We are currently in the process of screening these libraries for transpositional events in which the lac Z gene is induced or repressed by salicyl alcohol and in which the resistance of nalidixic acid is not increased by salicyl alcohol. A number of potential mutants have been identified and we are beginning to map and characterize them.